The present invention relates to a process for forming an interconnection in a semiconductor device, and relates more particularly, to a method of forming an interconnection in such a device by using a landing pad.
Interconnection technology in a semiconductor device can be divided into two steps, i.e., formation of a contact hole and formation of an interconnection. As a semiconductor device becomes highly-integrated, the width of the interconnection line becomes more narrow. When the horizontal size of the contact is reduced its vertical size is increased, which increases the aspect ratio of the contact. A metal interconnection needs to be multileveled to enable enhancing of the operation speed of a device and for reliability of the interconnection. Also, filling of a contact hole is essential for planarization of an interdielectric layer.
The filling techniques for filling contact holes in current multilevel interconnection formation processes consist mainly of either one of two methods. Such filling procedures usually involve either a physical vapor deposition method or a chemical vapor deposition (CVD) method.
The physical vapor deposition (PVD) method involves depositing in the contact hole a metal such as aluminum, for example, by sputtering. However, when the aspect ratio becomes increased by the reduction of a contact hole size to 1 .mu.m or less, the coverage-step of a metal deposited on the contact hole is degraded.
The CVD method of filling a contact hole is advantageous for obtaining an excellent step-coverage characteristic. But, the CVD method still presents difficulties when the method involves depositing aluminum in the contact hole.
Accordingly, a new method for filling the contact hole has recently been proposed. The new method comprises the steps of depositing aluminum by sputtering at a temperature and then reflowing the deposited aluminum at a high temperature of 500.degree. C.-550.degree. C.
However, as the aspect ratio of the contact hole becomes increased due to high-integration of a semiconductor, such as to 256M DRAM and 1 G DRAM, it is difficult to fill the contact hole. This difficulty is present even when the new aluminum reflow method is used to fill the contact hole for the formation of the metal interconnection layer.
Accordingly, due to the difficulties in filling the contact holes, the step-coverage of the metal interconnection is degraded and the contact resistances are increased.